The
GMAT
Critical
Reasoning
questions
are
meant
to test
your
understanding
of arguments
and
their
components.
An argument
is a
conclusion
supported
by evidence.
Each
Critical
Reasoning
question
on the
GMAT
is based
on a
stimulus
argument.
(Sometimes
there
are
two
questions
in a
row
that
are
based
on a
single
argument.)
The
questions
reward
those
who
can
recognize
well-constructed
arguments
or spot
flaws
in arguments.

CAUTION

These
questions are not knowledge questions.
So, take all "facts" at
face value and do not answer any
questions based on whatever prior
knowledge of the subject matter
that you may have.

Argument

There
are
really
only
two
parts
to an
argument: evidence and conclusion.
A mere
statement
alone
is neither
evidence
nor
conclusion.
For
example,
consider
the
following
statement:

Steve
wears
glasses.

This
statement,
without
anything
more,
is simply
a statement.
We don't
know
whether
it is
factual.
We don't
know
whether
the
author
of the
statement
is going
to reason
from
this
proposition
toward
a further
conclusion,
or whether
this
is the
ultimate
conclusion
that
the
author
is trying
to support.
We need
context
to determine
whether
this
statement
is evidence
or conclusion,
as follows:

Steve
wears
glasses.

People
who
wear
glasses
are
smart.

Therefore,
Steve
is
smart.

In
the
example,
the
original
statement, "Steve
wears
glasses," is
used
as evidence.
Note
that
we are
not
absolutely
sure
of the truth of
the
conclusion
because
we are
not
absolutely
sure
of the
truth
or falsity
of the
statement
that
people
who
wear
glasses
are
smart.
On the
other
hand,
the validity of
the
argument
is unassailable.
An argument
is valid
when
its
conclusion
is well
supported
by the
evidence
presented.

Alternatively,
the
original
statement
may
be supportedby
evidence rather
than used
as evidence,
as shown
in the
following
example:

Steve
is
nearsighted.

People
who
are
nearsighted
wear
glasses.

Therefore,
Steve
wears
glasses.

Again,
we are
not
100%
sure
of the
truth
of the
conclusion
because
at least
one
piece
of evidence
is questionable.
As we
are
all
aware,
not
all
nearsighted
people
wear
glasses.
Some
wear
contacts;
some
have
surgery.
(Some
drive
very
slowly
in front
of me
on the
freeway.)
However,
the
argument
is valid.
And,
it illustrates
that
the
original
statement, "Steve
wears
glasses," is
neither
evidence
nor
conclusion
on its
own,
and
can
be either
evidence
or conclusion,
given
the
proper
context.

Note
that
both
of the
arguments
include
two
pieces
of evidence.
This
is a
minimum
for
a properly
constructed
argument.
If you
try
to create
an argument
with
only
one
piece
of evidence,
you
leave
holes,
called assumptions.
For
example

Socrates
is
a
man.

Therefore,
Socrates
is
mortal.

This
one
has
been
around
for
thousands
of years.
It includes
an assumption.

TIP

Logicians define assumptions as suppressed premises because they call a piece
of evidence a premise.

The
assumption,
or unstated
evidence,
is that
all
men
are
mortal.
(In
Socrates' case,
this
was
proven
beyond
doubt
by a
hemlock
cocktail.)
So,
the
complete
argument
looks
like
this:

Socrates
is
a
man.

Men
are
mortal.

Therefore,
Socrates
is
mortal.

We
are
able
to derive
the
statement "Men
are
mortal," because
it is
the
only
statement
that
provides
a connection
between
the
unlike
terms
in the
original,
incomplete
argument.
Because
Socrates
appears
in both
the
first
piece
of evidence
and
the
conclusion,
linked
to two
different
words "man" and "mortal," we
need
a statement
linking
those
two
terms.

So,
assumptions
are
important
to understanding
arguments,
in that
assumptions
are
simply
unstated
evidence.

We
all
make
many
assumptions
every
day.
Some
are safe or warranted assumptions.
Others
are
a bit
shaky.
For
instance,
I can
usually
safely
assume
that
other
drivers
on the
road
are
going
to stick
to the
convention
of driving
on the
right
side
of the
road.
However,
it is
less
safe
to assume
that
a co-worker
has
the
same
political
beliefs
that
I do
or even
likes
the
same
sports
teams.